Some polishing apparatuses for polishing and planarizing a substrate such as a semiconductor wafer are capable of adjusting a pressure of a chamber in a carrier head. Such a polishing apparatus measures a physical quantity relating to a film thickness of a substrate and calculates a film thickness profile based on the physical quantity. Then, the polishing apparatus adjusts a pressure of a chamber in a carrier head based on a comparison between the calculated film thickness profile and a desired film thickness profile.
However, a conventional polishing apparatus does not perform a real-time control in which a pressure of a chamber in a carrier head is continuously adjusted during polishing. As a matter of course, a real-time control is expected to obtain polishing results that are closer to a desired thickness profile. When a real-time control is to be applied to a pressure adjusting method in a conventional polishing apparatus, a film thickness on a surface of a wafer or data that are substantially in proportion to the film thickness are required to be measured in situ. Accordingly, a real-time control is considerably limited in application depending upon types of films on a wafer or measurement methods.
Further, if a desired thickness profile is changed from moment to moment, complicated processes are required. If a desired thickness profile is fixed to a polished profile, manipulated variables become excessive or unstable particularly in a case where an initial film thickness is largely different from the desired thickness profile.